Question

Which among \(\text{F}_{2}\), \(\text{Cl}_{2}\), \(\text{Br}_{2}\) and \(\text{I}_{2}\) exhibit disproportionation reaction?

• A. \(\text{F}_{2}\) and \(\text{Cl}_{2}\)
• B. \(\text{Cl}_{2},\text{Br}_{2}\) and \(\text{I}_{2}\)
• C. Only \(\text{I}_{2}\)
• D. \(\text{F}_{2},\text{Cl}_{2}\) and \(\text{Br}_{2}\)

Hint:

Fluorine shows only the minus 1 state, so it cannot disproportionate, but chlorine, bromine and iodine can.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Disproportionation means the same element is oxidised and reduced at the same time, so it needs more than one oxidation state.

Step 2: Fluorine
Fluorine is the most electronegative element and shows only \(-1\) in its compounds.
It has no vacant d-orbitals, so it cannot go to positive states.

Step 3: Other Halogens
\(\text{Cl}_2\), \(\text{Br}_2\) and \(\text{I}_2\) can show positive oxidation states as well as \(-1\).
In alkaline medium they disproportionate, for example \(\text{Cl}_2+2\text{OH}^{-}\rightarrow\text{Cl}^{-}+\text{ClO}^{-}+\text{H}_2\text{O}\).

Step 4: Compare the options
The correct choice is \(\text{Cl}_2,\text{Br}_2\) and \(\text{I}_2\), which is option (B).

Final Answer:
Chlorine, bromine and iodine undergo disproportionation, but fluorine does not. \[ \boxed{\text{(B) }\text{Cl}_{2},\text{Br}_{2}\text{ and }\text{I}_{2}} \]